In an internal combustion engine, a constant torque can generally not be introduced into a powertrain having this internal combustion engine. Often, this is because periodic ignitions occur in the internal combustion engine and the energy released as a result is converted into a rotational movement of the crankshaft. Accordingly, the torque delivered by the crankshaft and the rotational speed of the crankshaft are both subject to fluctuations and oscillations which are referred to generally as rotational irregularities. Rotational irregularities of this kind may be noticeable in driving mode. Therefore, a general objective is to reduce or eliminate these rotational irregularities as far as possible.
Conventionally, by employing force accumulators or energy accumulators, i.e., for example, springs and correspondingly moving masses, the energies occurring in rotational irregularities of the kind mentioned above are temporarily stored and are then conveyed into the powertrain to achieve a smoother speed curve or torque curve. Likewise in pendulum masses known as speed-adaptive mass dampers, the rotational irregularities occurring in driving condition are converted into oscillating deflections of vibrating masses. The deflection takes place in opposition to centrifugal force and, by predefining the deflection path and the masses to be deflected, it is possible to tune to excitation speeds and excitation frequencies.
Because of the increasingly restricted space availability in modern vehicle construction, there is also less installation space available for the systems used for vibration damping. Therefore, corresponding loss of decoupling quality, i.e., the reduction of occurring rotational irregularities, can occur.
US2013/072338 describes a hybrid drive module with an electric drive component and a torsional vibration damper in the form of a spring-mass accumulator working on the principle of power splitting. The basic idea of power splitting consists in dividing the torque delivered by the internal combustion engine into two power branches, shifting their phasing with respect to one another, and subsequently superposing the two power branches to achieve a reduction in the rotational irregularities in the torque to be transmitted.
Systems of this kind have great technical complexity due to the large quantity of components and the complex interplay between the individual components. Thus there is a multitude of sometimes conflicting objectives in this technical field. It may therefore be advisable to coordinate this complex interplay, also in different operating conditions, to achieve as many advantages as possible with respect to efficiency and/or emissions.
For example, there is a need to find a better compromise between reducing rotational irregularities presenting a powertrain, reducing fuel consumption in a motor vehicle having the powertrain, and improving emissions and weight of the motor vehicle and the installation space available for the powertrain.